Fin heat exchanger

ABSTRACT

A plurality of iron tubes are positioned horizontal, parallel and across the top of a combustion chamber. An outer frame holds the tubes and directs the products of combustion about the outer side of the tubes. The interiors of the tubes are connected in series. The tubes are rectangular in cross-section. The first and last tubes of the series have their outer sides abutting and welded to adjacent sides of the frame. On these first and last tubes there are fins extending about only the top and the sides opposite said outer sides. Said fins are welded to the tube and to the frame. On the intermediate tubes there are fins extending about only the vertical sides and top sides of the tubes and being welded thereto.

e 1 ilmte States Patent 1191 1111 3,726,258 Reichmann et al. Apr. 10,1973 54] FIN HEAT EXCHANGER 780,565 1 1905 Humphrey ..122/367 [75]Inventors: Horst Reichmann, Wuppertal-El- "12233; beffeld; Rtlttmann,Wermel- 1,593,984 7/1926 Murray ..122/235 sklrchen, both of Germany2,877,000 3/1959 Person ..165/130 x 73 A h. V ill t KG sslgnee Jo a anPrimary Examinerl(enneth W. Sprague [22] Filed: Oct. 18, 1971Attorney-Darbo et al. [21] -Appl.No.: 190,094 ABSTRACT A plurality ofiron tubes are positioned horizontal, [30] Foreign Apphcanon Pnonty Dataparallel and across the top of a combustion chamber. Apr. 8, 1971Germany ..P 21 17 222.9 An u r fram h lds the tubes and directs the Nov.4, 1970 Austria .9940/70 Products of Combustion about the Outer Side Ofthe tubes. The interiors of the tubes are connected in se- 52 US. Cl.122/250 R, 122/367 c ries- The tubes are rectangular in eresseeetien-The [51] zz 27/06 first and last tubes of the series have their outersides 58 Field of Search 122/235 236 250 abutting and Welded to adjacentsides 0f the frame 122/367. 165/136 these first and last tubes there arefins extending about only the top and the sides opposite said outersides Said fins are welded to the tube and to the frame. On [56]References cued the intermediate tubes there are fins extending aboutUNITED STATES PATENTS only the vertical sides and top sides of the tubesand being welded thereto. 1,8l2,l98 6/1931 Clayton ..l22/367 X 3,388,6926/1968 Hale ..,.122/367 7 Claims, 9 Drawing Figures /8 I 7 5 7 8 '4 I 95444/ y 1 9 V v 72 s s P7771 n '77) n 77-; [X 7776 73 1e 5' S 711 I z 2275 20 t 2143 L l PATENTED 3.726258 SHEET 1 OF 3 Fig. 2

GEKNOT FOTTMANN IN V EN TORS FIN HEAT EXCI-IANGER BACKGROUND AND SUMMARYOF THE INVENTION This invention relates to a fin type heat exchanger ofrectangular or square shape as seen in a plan view. It comprises aplurality of finned tubes positioned parallel in a common plane. Thetubes are connected with each other to form a conduit through which thewater being heated flows. The finned tubes are mounted in and enclosedby a sheet metal frame which, throughout its circumference, is inheat-conducting communication with the fin tubes.

The prior art includes fin type heat exchangers which are enclosed by asheet metal frame (German Pat. application H 1 1,023 X/36e), the framesections through which the tubes pass being cooled by the tubes solderedto them. The sections of the frame parallel to the fin tubes transmittheir heat to the ends of the fin sections of the fin body connectedwith them for heat conduction as by welding. Moreover, downwardly theymerge with the combustion compartment of the gas-heated continuous-flowheater cooled by the heat exchanger coil. The heat exchanger coil iscapable of absorbing part of the heat from the sections of the frameparallel to the tin tubes. Nonetheless, in this prior arrangement heattransfer conditions are unfavorable.

Moreover, gas-heated continuous-flow heaters, respectivelycontinuous-flow heaters, have become prior art, which latter operatewith an oil gasification burner, and in which the fin body closes off acombustion compartment which iscooled on the outside by the air ofcombustion passed therepast and does not carry a heat exchanger coil.

It is an object of this invention, in a fin heat exchanger of the typeindicated hereinbefore, to improve the heat transfer conditions at thesections of the frame parallel to the fin tubes. According to theinvention, this object is attained by forming the fin tubes so as tohave a cross-section of upright rectangular configuration and bydirectly connecting these sections of the frame which are parallel tothe fin tubes with the outer side walls of the two outer fin tubes.

The embodiment of the invention is particularly advantageous if theframe 'of the fin block extends downwardly like a cap and is placed onthe upper rim of a combustion compartment cooled by the air ofcombustion directed therepast by a blower. The cap type extension of theframe directs the heating gas (products of combustion) to the fin body.The heat absorbed by the cap is transferred to the water in the tubes.From the frame sections through which the fin tubes are passed, the heatcan flow to the water through the welded joint between frame and fintubes. From the sections of the frame parallel to the fin tubes,according to the invention, the heat is transferred to the fin tubesthrough the shortest possible path in that these frame sections are infiat heat-conducting communication with the likewise flat outer sides ofthe two outer fin tubes. This provision is made because the hithertocommon end sections of the fins protruding relative to the outer fintubes and enclosing these tubes, cannot transfer the great heat volumeabsorbed by the cap additionally to the outer fin tube through their endedges, as in the prior arrangement heating gases still flow throughbetween the frame and the last fin tube and these fin areas are heatedanyhow by the heating gas.

Advantageously, the fin of the outer fin tubes fit only about the upperand free side of the tube and the rim of that portion of the fin whichextends over the fin tube is connected with the frame and the top sideof the fin tube as by welding. The fins of the intermediate tubes haverectangular recesses so that they fit on the fin tubes from above, andthe fins extend as far downwardly as the bottom edge of the fin tubes.These fins are connected with the respective tubes as by weldmg.

Another possibility of designing a fin body of the type indicated is toassemble the fin block in unit construction principle from singletube-fin sections and/or double tube-fin sections as well as from singletubeor double tube-end tube-fin sections with tubes terminating on oneside with a fin edge. Then, different fin heat exchanger types can bemanufactured from standard parts while maintaining the advantageousbasic design according to the invention. Thereby, the manufacture andstock keeping is simplified.

A convector is known per se comprising fin blocks including severaltubes arranged in one plane in juxtaposed relationship and connectedwith each other through which the heating water flows, the fin blocksbeing assembled from single tubeand double tube-fin sections. However,the fin tubes do not have an upright rectangular cross-section and thetin blocks do not have a frame which is directly connected with theouter side walls of the outer fin tubes. It is also not the point totransfer hat to a liquid flowing in the fin tubes. Hence, according tothe invention another construction element is added, namely an end fintube section with a tube terminating on one side with a fin edge.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section through the finbody of an embodiment of the invention;

FIG. 2 is a top or plan view of the embodiment of FIG. 1;

FIG. 3 is a vertical section through the fin block of anotherembodiment;

FIG. 4 is a plan view of the fin block of FIG. 3;

FIG. 5 is a section through a single tube-f'm component forming anintermediate tube;

FIG. 6 is a section through a double tube-fm component forming anintermediate tube;

FIG. 7 is a section through a single tube-fin component forming an endtube;

FIG. 8 is a section through a double tube-fin component forming an endtube; and

FIG. 9 is a longitudinal section through a fin tube of a fin block withframe section and its enlargement.

DESCRIPTION OF SPECIFIC EMBODIMENTS The following disclosure is offeredfor public dissemination in return for the grant of a patent. Althoughit is detailed to ensure adequacy and aid understanding, this is notintended to prejudice that purpose of a patent which is to cover eachnew inventive concept therein no matter how others may later disguise itby variations in form or additions or further improvements. The claimsat the end hereof are intended as the chief aid toward this purpose, asit is these that meet the requirement of pointing out the parts,improvements, or combinations in which the inventive concepts are found.

The fin tubes 1 of rectangular cross-section are positioned parallel, injuxtaposed relationship and in a common horizontal plane. The tubes areconnected with each other by elbows 2 to form a conduit from an inletconnection 3 to a discharge connection 4. At inlet 3, the water to beheated enters and after being heated it discharges through theconnection 4. The tubes 1 are equipped with fins 5. The fins have slotsextending upwardly from their bottom edges with tongues 6 between theslots. The slots are of a size to receive the tubes 1. Thus, in effect,the fins are fitted down over the top of the tubes with a part of thefin above the tubes and tongues 6 extending between the tubes. The finsabut the narrow sides 1 of the tubes at the top as at 7. The fins arewelded to the tubes. The term welding is used herein to include theprocedures sometimes referred to as soldering and brazing. The upperouter ends 8 of the fins fit about the tops of the two outer fin tubesand terminate coplanar with the outer flat sides 9 of the outer fintubes.

The fin block (formed by the assembly of the tubes 1 and the fins issurrounded by a rectangular sheet metal frame 10. The frame 10 has twoopposed sides 11 through which the fin tubes 1 pass. These sides 11 arein heat-conducting communication with the fin tubes as by means ofwelded joints. The other two frame sides 12 are in face-to-face contactwith the flat sides 9 of the outer two fin tubes and are welded to thelatter. lso, the ends 8 of the fins 5 are welded to the frame sides 9.

The rectangular frame 10 extends downwardly and becomes annular. Thus itis enlarged as at 13 beyond the centers of the frame sections andreduced in the area of the frame comers 14 (see FIG. 2). The annularbearing rim 15 thus formed is supported upon an annular upper rim 16 ofa casing 17 with the interposition of a seal 18. The inner wall 19defining a combustion compartment is cooled by the incoming air ofcombustion flowing in on all sides thereof to the burner of the heater.Thus, the inner wall 19 is surrounded by two concentric walls 20 and 17so as to define two outer annular channels 21 and 23 closed by anannular cap 22. Through the use of a blower 24, the air flows upwardlyin channel 21 and after returns downwardly through annular channel 23and is supplied to the burner (not shown) in the combustion chamber.

Thus, the walls 17, 19, 20, 22 define a housing about the combustionchamber which housing has air passageways about the outside of thechamber through which air flows to cool the walls. The cap l0, 13 servesthe function to direct the heating gases (products of combustion) fromthe cylindrical combustion chamber through the rectangular fin block.Due to the abutment of the frame sides 12 with the outer tubes, the heatabsorbed by the cap 10, 13 can be directly transmitted to the outer fintubes through the shortest possible path. This avoids an overheating ofthe frame. For use in an oil-heated water heater the fin block and frameis advantageously made of sheet iron. The lifetime of such a fin blockand frame exceeds by a multiple that of a fin block made from copper. Inthe combustion of oil the sulphur proportion is about 10 times theamount occurring in the combustion of petroleum derived gases. Sheetiron is sulphur-resistant as compared to copper.

In FIG. 3 the fin block is assembled from the single, intermediatetube-fin sections 31 and single, end tubefin sections 32. The tube-finsection 31 (see also FIG. 5) is comprised of a fin tube 33 rectangularin crosssection and having fins 34 mounted thereon. The tubefin sections32 (see also FIG. 7) are identical to each other and are comprised ofthe fin tube 33 and the end fins 35. The upper outer ends 36 of the fins35 fit over the inner and top sides of the outer fin tubes and terminatecoplanar with the outer fiat sides 37 of the tubes. The fin block isenclosed by a sheet metal frame 38, 39. The fin tubes 33 pass throughthe two sides 39 of the frame. These sides 39 are in heat-conductingcommunication with the fin tubes as by welding. The other two framesides 38 of the frame abut the fiat sides 37 of the outer fin tubes 33and are welded to the same. Also, the ends 36 of the end fins 35 arewelded to the frame sections 38. The rectangular frame 38, 39 extendsdownwardly and becomes annular, i.e. it is enlarged beyond the centersof the frame sides 38 and 39 as at 40 and reduced in the area of theframe comers 41 (see FIG. 4). The bearing rim 42 thus formed serves forplacement on an annular upper rim of a cylindrical sheet metal housing(not shown) enclosing the combustion chamber.

The cold water, or in a heating system the return flow water, isintroduced at the tube fitting 43 and the hot water (of a domestic watertap or a heating circuit supply) discharged through the fitting 44.Thus, a passageway is formed through the tubes from inlet 43 to outlet44. To this end, the fin tubes can be connected in pairs by caps 46,whereby the water flowing therethrough is directed from the one fin tubeto the other adjacent fin tube. The caps 46 are connected with the framesections 39 (as by welding) for this purpose. lnstead of two caps 46,one cap 47 can be used. This is welded to the frame sections 39similarly to the caps 46. It encloses a guide plate 48 which serves todirect the water flow from one tube to the adjacent tube.

According to the invention, fin blocks of different widths can beassembled from fin tube sections. By way of example, two intermediatefin tubes can be formed in pairs as double tube-fin sections (see FIG.6). Here, the fins 45 fit about the adjacent two tubes and are weldedthereto. Likewise, according to FIG. 8, the end tube (one or both) canbe joined with the first adjacent intermediate tube to form a doubleend-tube fin section.

With a single tube cross-section and with four fin shapes, fin blocks ofdifferent widths and, using longer tubes. of any desired length can beassembled. Such fin blocks are likewise suitable for combustion chambersof rectangular cross-section.

In FIG. 9 the tube 33 closely extends through the frame side 39 (whichfits closely thereabout) and terminates in the cap 47. The guide plate48 serves to direct the water from one tube to the next. The guide plate48 need not fully seal the guide path of the water relative to the innerwall of the cap. The frame side 39 extends downwardly into theenlargement 40 which forms the bearing rim 42 to rest upon the jacket ofthe combustion chamber (not shown). Fuel gas collecting hood 49 ismounted on the upper rim of the frame for discharge of the fuel gases.

We claim:

1. In a heat exchanger comprising a series of generally parallel tubescommunicating with each other, said tubes being elongated with thelength of said tubes being substantially in excess of their transversecross-sectional dimensions, said tubes having fins positionedtransversely to said length, a sheet metal frame for directing a heatedfluid across said finned tubes, said frame having sides inheat-conducting communication with said finned tubes, the improvementcomprismg:

said tubes being rectangular in transverse cross-section, one of saidsides of said frame being immediately adjacent the first of said seriesof tubes and being directly connected thereto, and another of said sidesof said frame being immediately adjacent the last of said series oftubes and being directly connected thereto.

2. In a heat exchanger comprising a series of generally parallel tubescommunicating with each other, said tubes having fins, a sheet metalframe for directing a heated fluid across said finned tubes, said framehaving sides in heat-conducting communication with said finned tubes,the improvement comprising:

said tubes being rectangular in transverse cross-section, one of saidsides of said frame being immediately adjacent the first of said seriesof tubes and being directly connected thereto, and another of said sidesof said frame being immediately adjacent the last of said series oftubes and being directly connected thereto, said one side being inface-to-face contact with a side of said first tube and is weldedthereto, and said other side is in face-to-face contact with a side ofsaid last tube and is welded thereto.

3. In a heat exchanger as set forth in claim 2, wherein said frame beingin the form of a cap with a downwardly extending rim.

4. The combination of a heat exchanger as set forth in claim 3 and ahousing defining a combustion chamber, said housing having an upperedge, said cap being seated on said upper edge, said housing havingperipheral walls with air passageways thereto leading to the point ofcombustion, and a blower connected to cause an air flow through saidpassageways to said point for the purpose of cooling said walls.

5. In a heat exchanger comprising a series of generally parallel tubescommunicating with each other, said tubes having fins, a sheet metalframe for directing a heated fluid across said finned tubes, said framehaving sides in heat-conducting communication with said finned tubes,the improvement comprising:

said tubes being rectangular in transverse cross-section, one of saidsides of said frame being immediately adjacent the first of said seriesof tubes and being directly connected thereto, and another of said sidesof said frame being immediately adjacent the last of said series oftubes and being directly connected thereto, said tubes having twovertical sides and two horizontal sides, the fins of the two outsidetubes of said series fitting about only one vertical and the tophorizontal sides of said tubes and being welded to the sides of theframe adjacent thereto and being welded to the 6. iii zfh eat exchangeras set forth in claim 5, wherein the fins of the intermediate tubes ofsaid series fit about only the top and the two vertical sides of saidintermediate tubes and are welded thereto.

7. In a heat exchanger as set forth in claim 1, wherein said tubes, saidfins and said frame are iron.

* =0 III l

1. In a heat exchanger comprising a series of generally parallel tubescommunicating with each other, said tubes being elongated with thelength of said tubes being substantially in excess of their transversecross-sectional dimensions, said tubes having fins positionedtransversely to said length, a sheet metal frame for directing a heatedfluid across said finned tubes, said frame having sides inheat-conducting communication with said finned tubes, the improvementcomprising: said tubes being rectangular in transverse cross-section,one of said sides of said frame being immediately adjacent the first ofsaid series of tubes and being directly connected thereto, and anotherof said sides of said frame being immediately adjacent the last of saidseries of tubes and being directly connected thereto.
 2. In a heatexchanger comprising a series of generally parallel tubes communicatingwith each other, said tubes having fins, a sheet metal frame fordirecting a heated fluid across said finned tubes, said frame havingsides in heat-conducting communication with said finned tubes, theimprovement comprising: said tubes being rectangular in transversecross-section, one of said sides of said frame being immediatelyadjacent the first of said series of tubEs and being directly connectedthereto, and another of said sides of said frame being immediatelyadjacent the last of said series of tubes and being directly connectedthereto, said one side being in face-to-face contact with a side of saidfirst tube and is welded thereto, and said other side is in face-to-facecontact with a side of said last tube and is welded thereto.
 3. In aheat exchanger as set forth in claim 2, wherein said frame being in theform of a cap with a downwardly extending rim.
 4. The combination of aheat exchanger as set forth in claim 3 and a housing defining acombustion chamber, said housing having an upper edge, said cap beingseated on said upper edge, said housing having peripheral walls with airpassageways thereto leading to the point of combustion, and a blowerconnected to cause an air flow through said passageways to said pointfor the purpose of cooling said walls.
 5. In a heat exchanger comprisinga series of generally parallel tubes communicating with each other, saidtubes having fins, a sheet metal frame for directing a heated fluidacross said finned tubes, said frame having sides in heat-conductingcommunication with said finned tubes, the improvement comprising: saidtubes being rectangular in transverse cross-section, one of said sidesof said frame being immediately adjacent the first of said series oftubes and being directly connected thereto, and another of said sides ofsaid frame being immediately adjacent the last of said series of tubesand being directly connected thereto, said tubes having two verticalsides and two horizontal sides, the fins of the two outside tubes ofsaid series fitting about only one vertical and the top horizontal sidesof said tubes and being welded to the sides of the frame adjacentthereto and being welded to the tubes.
 6. In a heat exchanger as setforth in claim 5, wherein the fins of the intermediate tubes of saidseries fit about only the top and the two vertical sides of saidintermediate tubes and are welded thereto.
 7. In a heat exchanger as setforth in claim 1, wherein said tubes, said fins and said frame are iron.